Robobass attempts luthiery - be afraid!

robobass · #1 02-03-2009, 02:31 PM

Hey all,
I have these 1/10 Roma basses I bought for teaching. They work well enough as beginner instruments for fifth graders, but they are fully carved, and I feel like they could be much more if they had higher bridges.

I placed 5mm shims under the bridge of the front one to see how the top would react. It doesn't sink at all, and the sound is much improved. The top seems quite strong and the bass bar high. I think I want to raise it even higher, but the action is already high. Neck reset? Out of the question for a <$500 bass. How 'bout a shim?

Turns out the FB was hardly attached at all, and whatever was there was not hide glue. It actually came off with denatured alcohol. I've got a pretty decent table saw, so I made up the wedge before attaching. Now how to get it back on the neck.

OK, this is maybe a bit out of control. I know I'm going to have problems keeping it in place once I start tightening the clamps, and I've never learned any standard techniques for dealing with it. I have some 1/8" pointed pins sticking out about 1mm. This way I can mark the back of the shimmed fingerboard, and drill corresponding holes into it. With the countersink I can remove those pins and switch them for longer ones for the actual gluing. Highly irregular I admit, but I think it will work.

What would a real repair guy do?

**Matthew Tucker** · #2 02-03-2009, 02:51 PM

you could use a couple of toothpicks as pins.

I usually make a box arrangement to clamp around the sides of the neck, lined with baking paper, so the sides of the box come up over the edge of the neck. then the FB doesn't slide around when glued and I have a flat back surface to clamp to.

I think a "proper luthier" would tend to glue the shim to the neck first, with STRONG glue, then flatten the shim, THEN glue the fingerboard. The shim is, after all, an adjustment to the neck.

**Damon Rondeau** · #3 02-03-2009, 02:58 PM

A little sturdier than a toothpick: a bamboo skewer.

Jake deVilliers · #4 02-03-2009, 04:11 PM

Round toothpicks would be perfect locating pins - they're usually birch or maple too!

Then a sequence as suggested by Matthew.

**Matthew Tucker** · #5 02-03-2009, 04:17 PM

yep them's the ones I was referring to.

draftsmann · #6 02-03-2009, 04:44 PM

I thought I was being quite clever (for a non luthier) when I used two steel pins to locate the fingerboard while gluing on my "Chinese parts bass" a while ago, until one of the clever chaps on this forum pointed out that they wouldn't be too kind to any plane used on the neck at a later date

I wish I'd used locating pins made from toothpicks. They would have done the job perfectly.

At least my board shouldn't have to come off for some time.

Adrian

arnoldschnitzer · #7 02-03-2009, 05:59 PM

Quote:

Originally Posted by Matthew Tucker

I think a "proper luthier" would tend to glue the shim to the neck first, with STRONG glue, then flatten the shim, THEN glue the fingerboard. The shim is, after all, an adjustment to the neck.

I glue the shim to the fingerboard first (square), then mill it to the taper I want, true things up, and glue the assembly to the neck. Works fine. If you glue on the shim first, then put a plane to it, you will run into the scroll cheeks and make a mess of them (because of the downward slant of the shim). Perhaps I'm not a "proper" luthier...

Jake deVilliers · #8 02-03-2009, 07:58 PM

Don't worry AHHNOLD, your impropriety will improve in time!

robobass · #9 02-04-2009, 03:52 AM

Quote:

Originally Posted by arnoldschnitzer

I glue the shim to the fingerboard first (square), then mill it to the taper I want, ...

I was told to glue the shim to the FB for exactly this reason (scroll). I made the taper first simply because it made the most sense with the tools available.
I think I'll stay with my metal pins. They will be far away from the surface of the board or the back of the neck. The only time they would be encountered again is if the FB is removed, which I doubt will ever happen. Also, I really don't see toothpicks resisting the shear force of heavy clamping, as I don't plan to make a holding box. I'll post pics when finished!

robobass · #10 02-04-2009, 10:19 AM

Finished!

Well, a little edge smoothing and varnish still to go, but I think it will come in at about 3-1/2 hours. With the pins it lined up like Lego blocks, and I had plenty of access to clean the glue splooges while they were hot. It will raise the bridge about 1 cm - just what I wanted!